1. Field of the Invention
The present invention relates to glazing panes for thermal insulation and/or protection against solar radiation, and more especially a glass substrate provided with functional thin films deposited under vacuum.
2. Discussion of the Background
Substrates having multifilms are useful as glass equipment for buildings or ships. In fact, by affecting the amount of energy of the solar radiation transmitted, excessive heating inside rooms, which in especially uncomfortable in summer, may be avoided, and thus the energy consumption required for the air conditioning of said rooms may be limited. This point is especially crucial in that the present-day tendency is to increase the proportion of the glazed areas on the facades of buildings.
There exist, however, other requirements which make such substrates having films very suitable for use in buildings, a primary requirement being the durability of the thin films, especially where the glazing panes are intended for use as monolithic glazing.
It is, in fact, important for this substrate coated with thin films to be suitable for use in monolithic glazing. This application implies that the thin films shall be wear-resistant over time, even without being protected an they would be in the interior of a laminated pane or a multiple glazing pane of the double glazing type. Now in a monolithic glazing, the thin films are directly subject to attack both of a mechanical nature, for example by friction creating scratches and leading to defects in appearance in transmission as well as in reflection, and to attack of a chemical nature, for example on contact with humidity and/or pollution of the surrounding atmosphere or when the pane is cleaned with chemical products.
Nor must a requirement of an aesthetic nature be forgotten; it is desirable that the glazings when viewed in external reflections shall be able to exhibit varying tints notably rather soft and pastel shades.
It is not usually necessary to have, for building construction, panes having a very high transmission of light as may be the case for an automobile, for example for windshields, but it is nevertheless advantageous to be able to offer types of glazing having different levels of light transmission.
With regard to the method of producing the thin films, the techniques of deposition under vacuum, notably using cathodic sputtering, are well known and enable the optical performances of the films obtained to be well controlled. In particular, those techniques are known which are carried out in the presence of a magnetic field, which multiplies the impacts of the ions on the target and accelerates the deposition. Mention may be made, for example, of Pat. DE-24 63 431 C2, which presents such a method using a planar magnetron, and of the U.S. Pat. No. 4,116,806, which utilizes a target in the form of a belt, known as a "belt track".
Similarly, reactive cathodic sputtering techniques are known, which enable a thin film to be produced by causing the material of the target to react with a gas of the plasma; U.S. Pat. No. 3,907,660 thus presents such a method for the deposition of metallic oxide on glass.
Among the thin metallic or other films acting upon solar radiation, notably by reducing the energy transmission, T.sub.E, both by absorption and by reflection, films based upon a chrome-nickel alloy or iron-chrome-nickel alloy are known. Thus, U.S. Pat. No. 4,022,947 presents more especially a substrate of glass provided with a film made from one of these alloys and a film of the oxide corresponding to said alloy. This oxide film is placed either on the functional film, itself deposited onto the substrate, or between the substrate and said functional film. In the former case, it has an essentially protective role, but without this protection being calculated. In the latter case, it has an essentially interferential role for the purpose of modifying the coloration on the glass side, but without the intensity thereof being indicated.
Thus, there remains a need for glass panes which are coated with thin films which can control the amount of energy transmission of solar radiation.